US regulators on Thursday warned about a number of US and foreign-owned websites aiming to sell or advertise dietary supplements which they claimed cure, treat or prevent diabetes.
The US Food and Drug Administration and the US Federal Trade Commission both said they sent warning letters to dozens of companies in addition to contacting government agencies in Mexico and Canada.
The two agencies said they discovered the sites through an "Internet sweep" for fraudulent sites and products.
Diabetes, a condition in which patients can have too-high blood sugar levels, affects nearly 21 million Americans and can be treated with diet, exercise, insulin shots and other medications. There is no cure.
"The internet can be a great source of information, but it also is a billboard for ads that promise miracle cures for diabetes and other serious diseases," Lydia Parnes, director of the FTC's Bureau of Consumer Protection, said in a statement. "Our advice to consumers: 'Be smart, be sceptical' when evaluating health claims online."
The FDA, which sent warning letters to 24 individuals and private companies, usually resolves such complaints without further action but the agency can impose fines and other civil penalties as well as seize products.
The FTC said about a quarter of the firms that were warned over deceptive ads - 84 US websites and seven Canadian sites targeting Americans - have changed their claims or shut down their sites.
The agency referred another 21 sites to other foreign governments.